During the first three decades of the 16th century Italy is the scene of almost ceaseless warfare between local contenders (particularly Venice and the papacy) and foreign claimants (France and Spain), with occasional interventions from north of the Alps by Habsburgs and by armies from the Swiss cantons.

The Italian adventures of the French king Charles VIII are continued by Louis XII, his cousin and successor. To the long-standing French claim to Naples, Louis adds a new demand - he believes himself to be duke of Milan, by descent from his Visconti grandmother.

French armies seize Milan for Louis XII in 1499, and the French occupy part of the kingdom of Naples in 1501. The Spanish soon recover full control of Naples (by 1504), but the presence of the French in Milan causes an ambitious new pope, Julius II, to intervene in the unstable affairs of northern Italy. He marches north and captures Bologna in 1506.

Julius believes Venice and the French to be the two main threats to the papal states of central Italy. With ruthless diplomatic skill he organizes two different alignments of the principal players, to deal with each of his enemies in turn.

The pope forms first the league of Cambrai, in 1508, in which he persuades France, Spain and the Austrian Habsburgs to join him against Venice. The Venetians are defeated at Agnadello in 1509, after which Julius and the Habsburgs appropriate much of Venice's mainland territory.

With this achieved, the pope moves on to his second objective. He organizes the Holy League of 1511. Again there is a single enemy, but this time it is France. Venice, recently humbled, is enrolled with Spain and the Habsburgs on the papal side; and there is useful support from the Swiss, now considered Europe's most formidable fighters. Even Henry VIII of England joins in, at a distance.

In 1512 a joint army of papal, Spanish and Venetian forces weakens the French in a battle near Ravenna, after which the Swiss are able to sweep through Lombardy and drive the intruders from Milan.

At this stage Venice and France are the clear losers. But this has only been round one. In the next bout, the contest becomes much more clearly a clash between Spain and France - and in particular a personal rivalry between two young kings. Francis inherits the throne of France in 1515. Charles, a Habsburg, becomes king of Spain in the following year on the death of Ferdinand II.

Francis I and Marignano: 1515-1519

A new mood of youth and enthusiasm enters France with the accession in 1515 of the 20-year-old Francis I. The centre of a glamorous young group of courtiers, he is a cousin of the previous king, Louis XII, and is married to Louis' daughter.

In a spirit of adventure, Francis takes up his father-in-law's ailing and expensive cause in northern Italy. In the summer of 1515 he rides south to recover Milan from the forces of the Holy League. In a two-day battle at Marignano in September, the French defeat the ranks of Swiss infantry - mercenaries, fighting in the pope's cause, whose pikes and halberds have previously seemed invincible.

French artilllery plays its part in the victory at Marignano, but the French cavalry also cuts a dash - with the young king prominent in person. In a mood of medieval chivalry, Francis is knighted on the battlefield by a famous French warrior, Pierre de Bayard, the brave victor in many past encounters and known in his own lifetime as the chevalier sans peur et sans reproche ('knight without fear or reproach').

The rapid capture of Milan, in the first year of his reign, makes Francis the most glamorous monarch in Europe. Leo X, the Medici pope who was funding the defeated Swiss mercenaries, entertains the victor of Marignano in lavish style at his papal court in Bologna.

Francis, liking what he sees of the Italian Renaissance (the pope offers him a madonna by Raphael), determines to enjoy these splendours. He invites Italian artists to France, including even the aged Leonardo da Vinci. By the spring of 1517 Italy's most versatile genius has moved to Amboise, where a rocky fortress has recently been adapted as a royal residence.

Leonardo lives the last two years of his life with the title 'first painter and engineer and architect' of the French king. But in the year of Leonardo's death, 1519, there is a serious challenge to the status now enjoyed by Francis as the premier monarch of Europe. Charles, the even younger head of the Habsburg dynasty, emerges as a rival.

Charles versus Francis: 1519

Charles succeeds in 1516 to the throne of Spain and in 1519 - on the death of his grandfather Maximilian I - to all the Habsburg territories including Burgundy. The result is that he rules much of the land to the immediate south and north of France. There is every chance that Charles (now aged nineteen) will also be elected to his grandfather's crown as German king and Holy Roman emperor - an office which has been held by the Habsburgs since 1438.

If that happens, north Italy and Germany will also owe allegiance to this powerful young ruler. Alarmed at the prospect of France being encircled, the French king, Francis, decides to contest the imperial election.

There is perhaps little chance of a French king being elected to rule an empire which in its origin included France but which has not done so for centuries. But Charles is taking no risks. He clinches the election by dispensing vast sums in bribes (borrowing the money from the Fuggers, to their great advantage and his lasting inconvenience). He is elected in June 1519 and crowned as German king at Aachen in 1520.

This is the first encounter in a rivalry between Charles and Francis which comes to dominate the politics of western Europe. It involves a large measure of personal animosity.

Charles versus Francis: 1520-1529

Francis, preparing to make war on his rival after Charles's election as emperor, attempts first to secure an important ally on his western flank - England's Henry VIII, the third in this trio of autocratic young rulers born within a few years of each other. If Francis is to march safely against Charles, he cannot in his absence risk Henry pressing his family's ancient claim to the throne of France, or even extending the territory round England's last remaining French possession, the pale of Calais.

Francis therefore invites Henry in 1520 to the spectacularly lavish meeting which becomes known as the Field of Cloth of Gold.

The conviviality of the Field of Cloth of Gold fails to deliver an English alliance (Henry immediately moves on to a less sumptuous but more fruitful meeting with Charles V in Kent, where each agrees to make no pact with Francis for at least two years). In 1521 Francis moves against Spanish land in the Pyrenees, beginning years of intermittent warfare.

In 1522 an imperial army drives the French out of Milan. Three years later Francis marches into Italy to reclaim his territory, with disastrous consequences. The French are heavily defeated at Pavia, in 1525, and Francis himself is taken prisoner. Soon he is in a fortress in Madrid, negotiating with Charles under duress.

After six months Francis secures his release from Madrid by giving up his claims to Flanders, Artois and Tournai in the Netherlands, to Milan, Genoa and Naples in Italy, and to the duchy of Burgundy. But he has little intention of keeping his word. Within two months of his return to France, in 1526, he has put in place a pact, the League of Cognac, allying himself with Venice and a new pope, Clement VII.

This time it is the pope who soon finds himself a prisoner. An imperial army, campaigning in Italy and containing large numbers of unpaid German mercenaries, marches in 1527 on the holy city of Rome.

Rome is sacked, looted and ravaged with the violence customary on such occasions. Rich citizens are seized for ransom; there are stories of nuns offered for sale on the streets. The pope manages to reach the security of the Castel Sant'Angelo where he shelters, a prisoner in all but name, until the imperial army is at last withdrawn from the city.

These violent events prompt the treaty of Cambrai, signed in 1529 and known as the 'ladies' peace' because its terms are negotiated between Francis's mother and one of Charles's aunts. It confirms the concessions made by Francis in Madrid, except that now Charles renounces his claim to the original duchy of Burgundy (only a small part of his Burgundian inheritance).

Charles versus Francis: 1529-1547

While coping with French hostility, Charles has other major concerns not shared by his rival - aggression from the Turks (on the empire's eastern frontier, and in the Mediterranean), and the Protestant unrest which is creating turmoil in Germany.

In 1529 (the year of the treaty between Charles and Francis) the Turks besiege Vienna and the pirate Barbarossa, working in alliance with the Turkish sultan, secures himself a base in Algiers. In 1530 Charles finds time to have himself formally crowned emperor by the pope in Bologna. Then he hurries north to negotiate with the Protestants at Augsburg. In 1531 Protestant princes form the League of Schmalkalden in opposition to Charles.

In these circumstances there is every reason for the two leading European monarchs, both Roman Catholic, to stand together. But Francis cannot accept the defeat implicit in the treaty of Cambrai. He now shocks contemporary opinion by negotiating with Protestants and even Muslims for an alliance against the Habsburg empire.

Francis goes to war twice more against Charles, in 1536-8 and 1542-4. The fate of Nice in 1543 suggests very well the bitter and improbable results of this royal rivalry. The Muslim ally of Francis in the siege of Nice (in the duchy of Savoy, which is part of the empire) is Barbarossa. The famous pirate, now a Turkish admiral, carries off 2500 Christians into captivity.

The legacy of Francis I: 1547

Although the loser in the long struggle with Charles V, Francis I leaves his mark on France in many ways. As in England and Spain at the same period, royal authority is strengthened during his reign with an increasingly centralized administration. And the royal splendour is reflected in art and architecture. Francis is the monarch, more than any other, who brings the Renaissance to France.

Leonardo da Vinci is the greatest artist attracted to the court of Francis I, but he is only one of many. And these artists adorn buildings which are now palaces, rather than royal castles or hunting lodges.

The centre of French court life is Fontainebleau, a royal hunting lodge almost entirely rebuilt by Francis I from 1527. Here he brings the Italian artists Rosso Fiorentino (in 1530) and Primaticcio (in 1532), who together establish a French style of mannerist painting known as the school of Fontainebleau. They are joined in 1540 by the goldsmith and sculptor Benvenuto Cellini, whose famous golden salt cellar is made at Fontainebleau.

Francis has earlier rebuilt Chambord, from 1519 - in name a castle on the Loire, in style a palace. In 1546 he begins to transform Paris's old royal castle, the Louvre, into yet another palace. France is later the home of absolute monarchy. In Francis I it has a foretaste of the theme.

Placards, Waldenses and chambre ardente: 1534-47

In the last few years of the reign of Francis I the persecution of Protestants within Catholic France grows more pronounced. The religious clash first becomes a prominent issue in France with the so-called 'affair of the placards' in 1534, when radical Protestants indulge in an unwise and intemperate gesture.

During the night of October 17 the streets of Paris and other towns are secretly plastered with posters mocking the sacrament of the mass. One is even found the next morning on the door of the bedroom in which Francis I is sleeping at Amboise.

Over the next few months there is an energetic rounding up of Protestants. Twenty-three are burnt at the stake before politics dampens religious fervour. Francis needs the friendship of German Lutheran princes.

In the 1540s there is a return to religious severity. It is prompted partly by the publication in 1541 of Calvin's French version of his Latin Institutes, in which he sums up his Protestant theology. His book is burnt in 1544, and the martyrdom of Protestants resumes - though not as yet in dramatic numbers. In 1555 Jean Crespin records their suffering in his Book of Martyrs, the equivalent of Foxe's influential volume in England.

The greatest outrage of the 1540s, the massacre of the Waldenses, cannot be blamed directly on Francis or on government policy. Local officials in Provence deliberately mislead the king in order to justify the persecution. The Waldenses, a medieval sect attracted by the ideals of reform, adopt a creed close to that of Calvin. In 1545 their villages are burnt and some 3000 men, women and children are massacred.

Religious policy becomes more rigid during the reign of Francis's son, Henry II. A special court (the chambre ardente, 'burning chamber') is set up in Paris in 1547 for the trying of heretics. The French Reformation is about to acquire its uniquely intense and political character.

Reformation in France: 1559-1572

France is affected by the Reformation in a manner and to an extent different from any other country. The reason is that the community is split from top to bottom on the issue; and the sides are so evenly balanced that a civil war based largely on religion lasts for four decades.

During the first half of the 16th century the reformed faith spreads among the ordinary people of France, encouraged by missionary priests trained in Geneva. The Protestants, who become known in France as Huguenots, are confident enough to organize in 1559 a national synod in Paris.

By this time there are powerful aristocrats in the Protestant camp, among them even members of the great Bourbon dynasty - a branch of the royal family, by distant descent from Louis IX. Their enemies are the Guise family, passionately committed to the Catholic cause. France's wars of religion in the 16th century are also a struggle between these rival camps.

In 1559, the year of the Protestant synod in Paris, Henry II dies (he is killed jousting in a tournament). For the next three decades the throne of France is occupied in succession by three of his sons. But the first two are in their teens when they inherit. The real power lies with the Guise family and with Henry's widow, Catherine de Médicis.

At first, in 1559, the Guises have the upper hand. The young king, Francis II, is married to Mary Queen of Scots - whose mother is a Guise. But Francis dies in 1560. With the accession of her second son, Charles IX, Catherine de Médicis becomes regent.

While sporadic warfare continues in France between Catholic and Protestant forces, Catherine's main concern is to retain a balance of power which will keep her family on the throne. To this end she arranges a marriage between her daughter, Margaret, and Henry of Navarre - the leading member of the Bourbon family. The wedding takes place in 1572. It is followed within a week by the atrocities of St Bartholomew's day.

From a massacre to a mass: 1572-1594

Many of France's Huguenot nobility are in Paris in August 1572 for the wedding of the princess Margaret and Henry of Navarre. Four days after the ceremony there is an assassination attempt on a leading Protestant, Admiral Coligny. It is probably planned by the regent, Catherine de Médicis, together with the Guise family. But the admiral is only wounded.

The bungled plot prompts Catherine to over-react. She orders a massacre of all the Huguenots in Paris. The killing begins before dawn on August 24, St Bartholomew's day. Shops are pillaged, families butchered. By the evening of August 25 the government calls a halt, but the mob is now out of control.

Other towns follow suit. Estimates of the dead vary, with a likely total of between 10,000 and 15,000 Huguenots killed. The bridegroom, Henry of Navarre, is spared - but he has to declare himself a Catholic.

It is more than three years before Henry escapes from the French court, resumes his Protestant faith and leads the Huguenot cause against a Catholic league headed by the Guise family. By now the stakes have been considerably raised. Catherine's second son, Charles IX, dies in 1574. Her third son succeeds him, as Henry III. He is childless, and in 1584 his only remaining brother dies. The Protestant Henry of Navarre is now heir presumptive to the French throne.

The last few years of the Valois dynasty are the stuff of melodrama. Henry III breaks his alliance with the Catholic faction in 1588 and has the two leading members of the Guise family assassinated. He then joins forces with Henry of Navarre. But the king is himself assassinated in 1589. On his deathbed he names his Protestant and very distant cousin as his successor - thus bringing the Bourbon dynasty to the throne of France.

It takes Henry of Navarre, now Henry IV, several years to conquer his kingdom. Paris, rigorously Catholic and strongly defended, is his main obstacle. It only yields to him, in 1594, after he has once again declared himself a Catholic - and this time for good.

It may well be that Henry IV never says the famous remark attributed to him on this topic (Paris vaut bien une messe, Paris is well worth a mass), but the sentiment is true to history. France's long religious wars are resolved by the simple expedient of making light of religion.

The compromise leaves Henry morally obliged to introduce religious toleration. His Edict of Nantes, signed in 1598, gives the Huguenots full civil rights, freedom of worship (within certain restrictions) and various agreed places which they can fortify for their protection. These concessions are violently resented by the Catholic majority. They will be steadily chipped away at, until the Edict of Nantes is finally revoked in 1685.

Henry IV: 1589-1610

After winning his kingdom in nine years of continuous war, Henry IV brings France twelve years of very productive peace. The state's finances are put on a sound footing, industry and commerce are encouraged (an ambitious scheme for a network of inland waterways includes the beginning of the Briare canal) and the army is strengthened.

In his foreign policy Henry takes the same conciliatory approach as with the bitterly opposed religious factions in France. His aim is to achieve peace on France's borders. To this end he helps to negotiate in 1609 the Twelve Years' Truce between Spain and the United Provinces.

Contrary to this principle, Henry decides to intervene in 1610 in a dispute over the inheritance of the duchy of Jülich, close to the sensitive border between the United Provinces and the Spanish Netherlands. The Habsburg emperor Rudolf II is about to seize the duchy, and Henry IV is about to march against him, when Henry is assassinated in a Paris street by François Ravaillac (a Catholic whose precise motives are unclear).

Henry is one of France's most popular kings. Four years after his death a bronze statue of him on horseback is erected on the Pont Neuf - Paris's most famous bridge, completed during Henry's reign in 1604 (and now the oldest in the city, in spite of its name).